Looking to add some hardscape
I'm fairly new to this hobby and I currently have a pretty boring planted 36 gallon bowfront tank. Now that I've gotten to the point where I can keep my fish and plants alive (for the most part) I'm looking to make it a little more presentable visually.
I currently just have all my plants growing from my flat substrate. I went to Home Depot the other day and picked up some slabs of flagstone (I did test them with some hydrochloric acid and got no fizzing.) My intention is to add some hardscape elements other than the one large piece of driftwood I currently have.
So my thought was to get the stone slabs nice and clean and then break them into smaller pieces and build a sort of mountain / cave in the back left corner of my tank. My plan is to build it up in layers, leaving a gap in the middle for fish to hide in.
My questions are:
1. Can I use hot glue to build one solid piece outside the tank? Is normal hot glue safe for aquarium use? will it hold up or fall apart? Is there something else I should be using?
2. An idea I had was to leave some depressed areas (maybe 2-3" deep or so) in the structure, then fill them with substrate and add some plants to the little "bed" areas. Will any plants live in such a small amount of substrate?
3. Is there a way to get some moss or other carpet-type plants to stick to the rock?
4. Do you have any other advice or ideas about a glued-together rock formation?
Thanks in advance for any and all input.